The invention relates to a device for monitoring a patient for rejection reactions of an implanted heart.
Rejection of the transplanted heart poses a serious problem in heart transplants. It is therefore important to diagnose an incipient rejection reaction as soon as possible in order to be able to initiate immunosuppressive treatment in proper time. Various methods are available for monitoring the patient for incipient rejection reactions of the implanted heart.
Tissue samples are removed from the transplanted heart by endomyocardiobiopsy, and examined histologically. Invasive removal of tissue samples can only be performed in specialized hospital settings. The test cannot be repeated as often as desired, so that there is a risk of a rejection reaction beginning during the time interval between two biopsies and developing into a clinically threatening rejection crisis. Moreover, the method is only moderately representative, since only a few tissue samples can be taken each time and so will not necessarily indicate that a rejection reaction has already begun.
An electrophysiological method is also known in which the intramyocardial electrogram is measured and its changes used to diagnose the rejection reaction. Diagnosis using an intramyocardial electrogram is subject to some uncertainties since the measurement results can be influenced by other factors including fluctuations in the circadian rhythm, the stress state of the patient, and medication.
Finally, monitoring heart function using echocardiography is known. This method, which determines the movement of the heart wall using an ultrasonic echo, can likewise only be performed in specialized clinics by trained personnel. The time intervals between tests are therefore necessarily relatively long and the test is expensive. The investigative method can also be made more difficult or even rendered impossible by emphysema or adiposity of the patient, for example.
A device that can be used to monitor a patient for rejection reactions of an implanted heart is known from U.S. Pat. No. 4,237,900. It is designed to monitor the pressure in the heart.
The goal of the present invention is to provide a device which makes it possible, at reasonable cost, continuously to monitor the function of a transplanted heart, especially to detect the movements of the heart wall.